Wrap tests/doctests into with_unicode(false)

[lgoettgens]

Needs Nemocas/AbstractAlgebra.jl#1586.

If one has unicode enabled and runs tests/doctests/doctest_fix locally, this may lead to inconsistent results (as the printing may use unicode).
This PR wraps all of these functions into a block that disables unicode temporarily to get consistent output.

[benlorenz]

I think calling it in each test_module will lead to race-conditions when running the tests in parallel since each allow_unicode will try to write to the same LocalPreferences.toml (twice). It would be good to have some way to override the setting without storing it.

[lgoettgens]

I didn't realize that test_module is called in runtests.jl, I thought this was just for interactive use

[fingolfin]

Regarding @benlorenz's comment, I've opened Nemocas/AbstractAlgebra.jl#1588

[lgoettgens]

Now that Nemocas/AbstractAlgebra.jl#1586 is available, there are no longer any race conditions between different workers as with_unicode now uses a global variable instead of the file.
allow_unicode(something; temporary=false) leads to weird effects if used in a test file (as it is called inside a with_unicode block in test_module). Thus, I adapted all of these to only change this temporarily.

[codecov]

Codecov Report

Merging #3271 (141794b) into master (968e9e4) will decrease coverage by 0.02%.
Report is 1 commits behind head on master.
The diff coverage is 43.75%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3271      +/-   ##
==========================================
- Coverage   81.81%   81.80%   -0.02%     
==========================================
  Files         556      556              
  Lines       74134    74150      +16     
==========================================
+ Hits        60653    60656       +3     
- Misses      13481    13494      +13     

Files	Coverage Δ
src/utils/tests.jl	67.77% <67.74%> (+0.36%)	⬆️
src/utils/docs.jl	1.17% <0.00%> (-0.05%)	⬇️

... and 2 files with indirect coverage changes

[benlorenz]

Thanks for taking care of this, seems to work fine.

I did some local tests with several Oscar instances using the same directory, running with many workers and tests + doctests in parallel.